Complex Plasmas as a Model for Complex Plasmas as a Model for

the Quark-Gluon-Plasma Liquidthe Quark-Gluon-Plasma Liquid

Markus H. Thoma*

Max-Planck-Institute for Extraterrestrial Physics

1. Strongly Coupled Plasmas

2. Complex Plasmas

3. Applications to the Quark-Gluon Plasma

* Supported by DLR (BMBF)

1.1. Strongly Coupled PlasmasStrongly Coupled Plasmas

Plasma = ionized gas, 99% of visible matter in Universe

Plasmas generated by high temperatures, electric fields, or radiation

Classifications:1. Non-relativistic – relativistic plasmas (pair plasmas, QGP)2. Classical – quantum plasmas (white dwarfs, QGP)3. Ideal – strongly coupled plasmas (complex plasmas, QGP)

Coulomb coupling parameter

Td

Q2

Q: charge of plasma particlesd: inter particle distanceT: plasma temperature

Ideal plasmas: most plasmas:

Strongly coupled plasmas:

Examples: ion component in white dwarfs, high-density plasmas at GSI

Non-perturbative description, e.g., molecular dynamics

One-component plasma, pure Coulomb interaction (repulsive):

> 172 Coulomb crystal

Debye screening Yukawa systems

Additional parameter: d/D

Drer

QrV /)(

Liquid phase:

Purely repulsive interactionno gas-liquid transition,only supercritical fluid

2. Complex Plasmas2. Complex Plasmas

Dusty or complex plasmas = multi component plasmas containingions, electrons, neutral gas, and microparticles, e.g., dust

Example: low temperature neon plasma in a dc- or rf discharge

Injection of microparticles with diameter 1 – 10 m

High electron mobility microparticlescollect electrons on surface largenegative charge: Q = 103 – 105 e

Inter particle distance about 200 m

plasma crystal (predicted 1986, discovered 1994 at MPE)

Observation: illumination by laser sheet and recorded by CCD camera

Melting of plasma crystal by pressure reductionless neutral gas friction temperature increase decrease of Coulomb coupling parameter Q2/(dT)

Quantitive analysis of equation of state and determination of : pair correlation function

)(1

)( ji

N

ji

rrrN

rg

Crystal: long range order sharp peaks at the nearest neighbors, next to nearest neighbors and so on

Liquid: short range order (incompressibility) only one clear peak corresponding to inter particle distance plus one ortwo broad and small peaks

Gas: no order no clear peaks

Gravity has strong influence on microparticles microgravity experiments

Applications of complex plasmas:

1. Model system for phase transitions, crystallization, dynamical behavior of liquids and plasmas on the microscopic level

2. Astrophysics: comets, interstellar plasmas, star and planet formation, planetary rings, …

3. Technology: plasma coating and etching, e.g. microchip production, problem: dust contamination

3. Applications to the Quark-Gluon 3. Applications to the Quark-Gluon PlasmaPlasma

Td

C S2Estimate of interaction parameter

C = 4/3 (quarks), C = 3 (gluons)200MeV S = 0.3 - 0.5 d = 0.5 fmUltrarelativistic plasma: magnetic interaction as important as electric

1.5 – 6 QGP Liquid?

RHIC data (hydrodynamical descriptionwith small viscosity, fast thermalization) indicate QGP Liquid

Attractive and repulsive interaction gas-liquid transition at a temperatureof a few hundred MeV

Static structure function (Fourier transform of pair correlation function) experimental and theoretical analysis of liquids

Hard Thermal Loop approximation (T >> Tc):

rmDfD

D

f Der

m

n

TNrggTm

mp

p

n

TNpS

23

22

23

2)(,

2)(

interacting gas

QCD lattice simulations QGP liquid?

Strongly coupled plasmas cross section enhancement

Reason: Coulomb radius, rC = Q2/E, larger than Debye screening lengthD = 1/mD modification of Coulomb scattering theory enhancement of ion-microparticle interaction (ion drag force)

QGP: rC /D = 1 – 5 parton cross section enhancement by factor 2 – 9small mean free path (corresponding to small viscostity and fastthermalization. Additional cross section enhancement by non-linear and non-perturbativeeffects

Implication: enhancement of collisional

energy loss, suppression of radiative energy loss byLPM effect (formation time) jet quenching

,E

dx

dE

coll

Conclusions Conclusions

• Strongly coupled plasmas are of increasing importance in fundamental research as well as technology

• QGP and complex plasmas are important examples of strongly coupled plasmas

• QGP is the most challenging strongly coupled plasma

• Complex plasmas can easily be studied and used as a model for the QGP (phase transitions, correlation functions, cross sections, …)

• RHIC and ISS provide very important information on strongly coupled plasmas